Equipment for dispensing chemical additives and admixtures into concrete is conventionally based on volumetric measurement. Such equipment includes mechanical fluid meters, sight bottles as visual indicators, control elements, bladder tanks, tubing, valves and pumps. Volumetric systems require consideration of the viscosity of the various fluids to be dispensed, and the viscosity can vary considerably depending on temperature and other factors.
Mechanical fluid meters are often problematic due to their moving parts and due to the effects of chemical attack on the numerous parts. Sight bottles are typically constructed out of steel or acrylic, and are calibrated. The sight bottles need to be located at or near the concrete batching office or otherwise monitored closely by visual means. This usually requires that extensive tubing be run from the dispensing location to the batching office. Throughout the concrete ready-mix industry, the various components of concrete such as cement, sand, aggregates, and water are weighed to determine the proper amount for batching, and hence volumetric dispensing of admixtures presents an additional procedural step, for which additional hardware and personnel training is required.
In U.S. Pat. Nos. 5,224,626 and 5,377,868 (owned by the assignee hereof), Hernandez et al. taught an apparatus and method for dispensing admixtures based upon weight so as to avoid the additional procedural step of measuring volumetrically. In one embodiment of this dispensing system, one or more admixture storage containers are supported by a suspended platform. In another embodiment, brackets are used for suspending the containers. A weight sensing system such as a single load cell is used for weighing the contents of the admixture storage containers. The platform or brackets are arranged so that the load cell is responsive to less than 100% of the weight in the containers. The containers are filled to a predetermined weight, and the contents are dispensed from each container in series or simultaneously. The weight sensing system of Hernandez et al., however, has not been commercially adopted in the ready-mix industry, which continues to employ volumetric measurement as a predominant practice.
It is therefore among the objectives of the present invention to provide a novel apparatus and process for dispensing concrete admixtures or other dispensable fluids, with enhanced accuracy, reliability, durability, cost-effectiveness, convenience in installation, and serviceability.
It is a further objective to provide an apparatus and processes for dispensing fluids of varying viscosities. The invention may be used to dispense paints and pigments, particle suspensions, fiber suspensions, and other fluids that may have extremely high viscosities, such as gels and pastes, and even gels and pastes having suspended particles, fibers, or other materials.